Interleukin-4 (IL-4) is a pleiotropic cytokine that has a broad spectrum of biological effects on lymphoid B and T cells, and many non-lymphoid cells including monocytes, endothelial cells and fibroblasts. For example, IL-4 stimulates the proliferation of several IL-2- and IL-3-dependent cell lines, induces the expression of class II major histocompatability complex molecules on resting B cells, and enhances the secretion of IgG4 and IgE by human B cells. IL-4 is associated with a Th2-type immune response, and is produced by and promotes differentiation of Th2 cells. IL-4 has been implicated in a number of disorders, such as allergy and asthma.
IL-13 is a recently identified (Minty, A. et al., Nature, 1993, 362, 248-250, and McKenzie, A. N. et al., Proc. Natl. Acad. Sci. U.S.A, 1993, 90, 3735-3739) cytokine of 112 amino acids secreted by the activated T lymphocytes, the B lymphocytes and the mastocytes after activation.
By virtue of its numerous biological properties shared with IL-4, IL-13 has been described as an IL-4-like cytokine. Its activities are indeed similar to those of IL-4 on the B cells (Defiance, T. et al., J. Exp. Med., 1994, 179, 135-143, Punnonen, J. et al., Proc. Natl. Acad. Sci. (USA), 1993, 90, 3730-3734, Fior, R. et al., Eur. Cytokine Network, 1994, 5, 593-600), the monocytes (Muzio, M. R. F. et al., Blood, 1994, 83, 1738-1743, De Waal Malefyt, R. et al., J. Immunol, 1993, 151, 6370-6381, Doyle, A. et al., Eur. J. Immunol. 1994, 24, 1441-1445, Montaner, L. J. et al., J. Exp. Med., 1993, 178, 743-747, Sozzani, P. et al., J. Biol. Chem., 1995, 270, 5084-5088) and other non-haematopoietic cells (Herbert, J. M. et al., Febs Lett., 1993, 328, 268-270, and Derocq, J. M. et al., Febs Lett. 1994, 343, 32-36). On the other hand, contrary to IL-4, it does not exert a specific effect on resting or activated T cells (Zurawuki, G. et al., Immunol. Today, 1994, 15, 19-26).
Various biological activities of IL-13 on the monocytes/macrophages, the B lymphocytes and certain haematopoietic precursors have been described in detail by A. J. Minty as well as in review articles on IL-13. Several data indicate, in addition, that this cytokine has a pleiotropic effect on other cell types. These non-haematopoietic cells which are directly affected by IL-13 are endothelial and microglial cells, keratinocytes and kidney and colon carcinomas.
One of the stages in the analysis of the signal transmitted by a biological molecule within a cell consists in identifying its membrane receptor. The research studies carried out to this end on the IL-13 receptor have shown that IL-13 and IL-4 have a common receptor, or at the very least some of the components of a common receptor complex, as well as common signal transduction elements (Zurawski S. M. et al., Embo Journal, 1993, 12, 2663-2670, Aversa, G. et al., J. Exp. Med., 1993, 178, 2213-2218, Vita, N. et al., Biol. Chem., 1995, 270, 3512-3517, Lefort, S. et al., Febs Lett., 1995, 366, 122-126). This receptor is present at the surface of various cell types, in a variable number according to the cell type considered. The comparative distribution of the IL-13 and IL-4 receptors has been indicated by A. J. Minty (Interleukin-13 for Cytokines in Health and Disease. Eds D. G. Remick and J. S. Frie, Marcel Decker, N.Y. 1996).
The cell surface receptors and receptor complexes bind IL-4 and/or IL-13 with different affinities. The principle components of receptors and receptor complexes that bind IL-4 and/or IL-13 are IL-4Rα, IL-13Rα1 and IL-13Rα2. These chains are expressed on the surface of cells as monomers or heterodimers of IL-4Rα/IL-13Rα1 (Type II IL-4R) or IL-4Rα/γc (Type I IL-4R). IL-4Rα monomer and IL-4Rα/γc heterodimer bind IL-4, but not IL-13. IL-13Rα1 and IL-13Rα2 monomers bind IL-13, but do not bind IL-4. IL-4Rα/IL-13Rα1 heterodimer binds both IL-4 and IL-13 (Murata et al., Int. J. Hematol., 1999, 69, 13-20).
Th2-type immune responses promote antibody production and humoral immunity, and are elaborated to fight off extracellular pathogens. Th2 cells are mediators of Ig production (humoral immunity) and produce IL-4, IL-5, IL-6, IL-9, IL-10 and IL-13 (Tanaka, et, al., Cytokine Regulation of Humoral Immunity, 251-272, Snapper, ed., John Wiley and Sons, New York (1996)). Th2-type immune responses are characterized by the generation of certain cytokines (e.g., IL-4, IL-13) and specific types of antibodies (IgE, IgG4) and are typical of allergic reactions, which may result in watery eyes and asthmatic symptoms, such as airway inflammation and contraction of airway muscle cells in the lungs.
Both IL-4 and IL-13 are therapeutically important cytokines based on their biological functions and play critical roles in many diseases, including asthma (Curr Opin Allergy Clin Immunol 2005, Vo. 5, 161-166). IL-4 has been shown to be able to inhibit autoimmune disease and IL-4 and IL-13 have both shown the potential to enhance anti-tumor immune responses. Since both cytokines are involved in the pathogenesis of allergic diseases, inhibitors of these cytokines could provide therapeutic benefits.
Accordingly, a need exists for improved agents that inhibit IL-4, inhibit IL-13, and single agents that inhibit both IL-4 and IL-13.